Merged SFR Product Fills Radar Gap over Northeastern NM

A powerful jet stream approached NM from the Pacific Northwest on February 23, 2016 and carved out a large scale upper level trough over the southern Rockies. Meanwhile, a strong area of surface high pressure raced southward down the front range of the Rockies and provided an influx of moist, cold air into eastern NM. Winter storm warnings were issued for several counties in northeastern NM with winter weather advisories in a few surrounding zones. Forecasters were eagerly anticipating how the event would unfold on the merged SFR product given the recent stretch of very dry and exceptionally warm weather. Figure 1 below is a Graphical Briefing issued prior to the event with expected snowfall totals.

Figure 1. Graphical Briefing issued prior to the expected snowfall event over northern and central New Mexico.

Figure 1. Graphical Briefing issued prior to the quick hitting winter storm event over northern and central New Mexico.

Rain and high terrain snow developed from north to south late on the 22nd before transitioning to all snow early on the 23rd. Forecast models from the 21st indicated that an area of heavy snow would impact northeastern NM on the 23rd. Figure 2 shows a well-defined axis of higher snowfall rates stretching from Trinidad, CO to Capulin, NM and Tucumcari, NM in the stand-alone SFR product from 0912 UTC 23 February 2016. Sampling this area showed peak liquid equivalent values near 0.07″/hr. The 0900 UTC observation at Trinidad showed the visibility had fallen to 1/2 mile within the snow band while the observation at Raton, NM showed no snowfall where the SFR product had near zero values. Farther south near Tucumcari the observation showed unknown precipitation falling at a temperature of 36° south of the main snow band.

Figure 2. Snowfall Rate product from 0912 UTC 23 February 2016 over northeastern NM. An area of higher snowfall rates is shown stretching from near Trinidad, CO to Capulin, NM and Tucumcari, NM.

Figure 2. SFR product from 0912 UTC 23 February 2016 over northeastern NM. An area of higher snowfall rates is shown stretching from near Trinidad, CO to Capulin, NM and Tucumcari, NM. Values peaked near 0.07″/hr.

The following merged SFR image at 0940 UTC showed the area of higher snowfall rates persisting (Figure 3 (left)). A merged SFR product from 0950 UTC is shown to note the extent of the radar void area (Figure 3 (right)). The following stand alone SFR product at 1245 UTC indicated the higher rates had shifted farther south but were still impacting at least portions of this same area (Figure 4). In this example the observation at Las Vegas, NM was indicating snowfall with visibilities down to 1 1/4 miles while Tucumcari showed very light snow with no values on the SFR product.

Figure 3. Merged SFR product from 0940 UTC (left) and 0950 UTC (right) showing snowfall detection in radar void area of northeastern New Mexico.

Figure 3. Merged SFR product from 0940 UTC (left) and 0950 UTC (right) showing snowfall detection in radar void area of northeastern New Mexico.

Figure 4. SFR product valid 1245 UTC 23 February 2016 showing higher snowfall rates persisting over northeastern NM.

Figure 4. SFR product valid 1245 UTC 23 February 2016 showing higher snowfall rates persisting over northeastern NM.

Based on the peak values depicted in the SFR product and the persistence of the snow band in the area forecasters were anticipating snowfall reports in the 2 to 6 inch range. The Snow-Cloud RGB product later in the day in Figure 5 verified this area of snowfall very well (red shades). Spotters reports are overlaid on the RGB imagery. Feedback from forecasters during this event supported accurate observations of the SFR product during the transition from rain to snow as well.

Figure 4. Snow-Cloud RGB product from 2014 UTC 23 February 2016 showing a band of snowfall over northeastern NM overlaid with spotter reports.

Figure 5. Snow-Cloud RGB product from 2014 UTC 23 February 2016 showing a band of snowfall over northeastern NM overlaid with spotter reports.

2 thoughts on “Merged SFR Product Fills Radar Gap over Northeastern NM

  1. Thanks for taking the time to make this post ABQ! This example was informative and can help others new to the product as well as the product developers. One thing I did want to point out…the SFR data shown are the liquid equivalent values. Have you had time to assess the liquid/snow ratios for this event in that area? Thanks!

  2. Forecasters felt the 10:1 ratios looked the most accurate on the SFR conversion. On the southern end of the snow band it was likely less than 10:1 since some melting occurred with warm surface temps.

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